CAREER: ERASE-PFAS: Mechanistic Investigation of Thermal Decomposition of Poly- and Perfluoroalkyl Substances in the Soil Environment

The contamination of soil and water by per- and polyfluoroalkyl substances (PFAS) is a national concern. Certain PFAS chemicals have been detected in the blood of more than 95% of the US population. Soil largely contributes to the quality of groundwater and crops, which are potential human exposure pathways for these chemicals. The challenge of dealing with PFAS contamination results from their chemical structure that leads to strong resistance to biological degradation in the environment. However, thermal processes such as forest fires are known to induce physical and chemical changes of PFAS chemicals in soil. The goal of this CAREER project is to understand the stability and decomposition of PFAS chemicals in soil during thermal treatment. A deeper understanding of these processes is necessary for the development of thermal technologies to clean up soils contaminated by PFAS for the protection of human and ecological health. Successful completion of this research will enable scientists to accurately predict decomposition products of PFAS in various thermal processes. Additional benefits to society result from the training of engineering undergraduates and enhanced learning through participation in hands-on experiments in soil chemistry and physics. Further benefits will accrue from the dissemination of results to the public, remediation professionals, and other stakeholders through outreach, conference presentations, and journal publications. This project is jointly funded by the CBET Environmental Engineering program and the Established Program to Stimulate Competitive Research (EPSCoR). The goal of this CAREER project is to elucidate transformation mechanisms of PFAS in soil during thermal treatment. PFAS reaction pathways at elevated temperatures will be identified through stepwise experiments assessing the thermal treatment of various PFAS classes under different gas phases in various soils and reference soil components. Results will be used to determine the combined effects of soil properties, PFAS molecular structure, and ambient atmosphere on degradation pathways; information critical to assessing thermal treatment as a potential remediation method for PFAS-contaminated soils. A novel aspect of this research arises from the use of an innovative identification approach based on continuously interleaving scans at low and high collision energies of time-of-flight mass spectrometry. Successful completion of this research will yield critical insight into the thermal stability of various classes of PFAS, enhanced understanding of the fate of PFAS in the soil environment during forest fires, and elucidation of mechanisms of thermal decomposition of PFAS. This knowledge is potentially transformative because the high thermal stability of PFAS is an implicit assumption in current environmental fate and transport models. The educational objectives of this project are focused on advancing STEM understanding through the involvement of undergraduate students in well-designed projects. Students will apply knowledge learned in class to address interesting and relevant real-world problems. The diversity of the Nation’s STEM workforce will be broadened through the participation of underrepresented groups in the research. This project is jointly funded by Environmental Engineering program of CBET and the Established Program to Stimulate Competitive Research (EPSCoR). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.